Metal particles from hip implants can get into the bloodstream, but it’s unclear whether the levels are high enough to cause problems—so the Food and Drug Administration wants implant makers to find out.
The FDA issued orders on May 6 to 21 companies that make metal-on-metal hip systems asking them to further study the safety of their devices. In particular, cobalt and chromium may be getting into the bloodstream.
Metal in the blood can cause problems elsewhere—the agency says on its website that small numbers of patients have had heart, nervous system or thyroid gland problems that may have been the result of metal ions in the bloodstream.
But not much is known about how large this risk is, as the FDA sums up in the article “Concerns about Metal-on-Metal Hip Implant Systems”:
“Different people will react to these metal particles in different ways. At this time, it is not possible to know who will experience a reaction, what type of reaction they might have, when the reaction will occur, or how severe the reaction will be. However, it is known that over time, the metal particles around some implants can cause damage to bone and/or tissue surrounding the implant and joint.”
Total hip replacements have three metal parts—a ball, a stem in the femur and a cup in the hip bone. The agency has a good diagram here. If patients feel pain, swelling or a change in walking ability, orthopedic surgeons can assess metal levels through blood tests, removing fluid from the joint with a needle or imaging the joint.
Hip replacement surgery, like any surgery, carries risks -- and metal-on-metal replacements have much to offer.
But patients who’ve developed a new condition or had general changes in their health since getting their surgery should pay special note to this issue. And, of course, talk to their doctor if concerned.
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